• KIISE Transactions on Computing Practices
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• v.22 no.2
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• pp.101-106
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• 2016

A femtocell network has been attracting attention as a promising solution for providing high data rate transmission over the conventional cellular network in an indoor environment. In this paper, we propose a distributed power control algorithm considering both indoor coverage and data load balancing in the femtocell network. As data traffic varies by time and location according to user distribution, each femto base station suffers from an unbalanced data load, which may degrade network performance. To distribute the data load, the base stations are required to adjust their transmission power dynamically. Since there are a number of base stations in practice, we propose a distributed power control algorithm. In addition, we propose the simple algorithm to detect the faulty base station and to recover coverage. We also explain how to insert a new base station into a deployed network. We present the simulation results to evaluate the proposed algorithms.

• Annual Conference of KIPS
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• 2013.05a
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• pp.187-188
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• 2013

비트토렌트는 인터넷을 통해 빠르고 효율적으로 파일을 공유할 수 있는 P2P (Peer-to-Peer) 파일전송 프로토콜이다. 파일을 P2P 네트워크 상에 분산하여 저장하고 서로 다른 환경의 피어들이 각자의 필요에 따라 쉽게 네트워크를 떠날 수 있기 때문에, 비트토렌트 네트워크는 매우 복잡하고 동적인 구조를 가진다. 본 연구에서는 이러한 네트워크 구조, 특히 피어들 간의 링크생성과 분리를 예측하여 비트토렌트 파일공유 시스템의 성능을 향상시키고자 하는 방향을 제시한다. 토렌트 크롤러 비트토렌트 네트워크 모니터링 시스템을 사용해 네트워크 부하를 최소화하며 네트워크 트래픽을 분석하고, 관찰된 네트워크 트래픽 특성을 통해 링크를 예측하는 방법을 제안한다.

• The Journal of the Korea Contents Association
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• v.9 no.9
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• pp.31-40
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• 2009

What are important in wireless sensor networks are reliable data transmission, energy efficiency of each node, and the maximization of network life through the distribution of load among the nodes. The present study proposed DSPR, a dynamic unique path routing machanism that considered these requirements in wireless sensor networks. In DSPR, data is transmitted through a dynamic unique path, which has the least cost calculated with the number of hops from each node to the sink, and the average remaining energy. At that time, each node monitors its transmission process and if a node detects route damage it changes the route dynamically, referring to the cost table, and by doing so, it enhances the reliability of the network and distributes energy consumption evenly among the nodes. In addition, when the network topology is changed, only the part related to the change is restructured dynamically instead of restructuring the entire network, and the life of the network is extended by inhibiting unnecessary energy consumption in each node as much as possible. In the results of our experiment, the proposed DSPR increased network life by minimizing energy consumption of the nodes and improved the reliability and energy efficiency of the network.

• The KIPS Transactions:PartC
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• v.14C no.6
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• pp.519-524
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• 2007

One of the most important issues on the sensor network with resource limited sensor nodes is prolonging the network lifetime by effectively utilizing the limited node energy. The most representative mechanism to achieve a long lived sensor network is the clustering mechanism which can be further classified into the single hop mode and the multi hop mode. The single hop mode requires that all sensor nodes in a cluster communicate directly with the cluster head(CH) via single hop md, in the multi hop mode, sensor nodes communicate with the CH with the help of other Intermediate nodes. One of the most critical factors that impact on the performance of the existing multi hop clustering mechanism is the cluster size and, without the assumption on the uniform node distribution, finding out the best cluster size is intractable. Since sensor nodes in a real sensor network are distributed non uniformly, the fixed size mechanism may not work best for real sensor networks. Therefore, in this paper, we propose a new dynamic size multi hop clustering mechanism in which the cluster size is determined according to the distance from the sink to relieve the traffic passing through the CHs near the sink. We show that our proposed scheme outperforms the existing fixed size clustering mechanisms by carrying out numerical analysis and simulations.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10a
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• pp.457-459
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• 1999

자율적 객체(autonomous object)는 분산 시스템에서의 기능(functionality)에 대한 융통성과 동적 확장성을 제공하기 위해 적합한 패러다임이다. 코드 이동성에 근거한 기능의 동적 합성이 자율적 객체에 의하여 지원되면 사용자의 다양한 서비스 요구 충족과 네트워크 부하 및 서비스 응답 시간 최적화 등과 같은 잇점을 얻을 수 있다. 본 논문에서는 이러한 잇점을 제공하는 코드 이동성에 기반한 동적 기능 합성에 대한 연구로서 기존의 연구들에서 제안하는 동적 기능 합성을 확장하고, 확장된 합성 메커니즘을 실현하기 위한 언어적 구조체(language constructs)를 설계하였다. 또한, 자율적 객체가 수행되는 환경으로서의 플랫폼을 제안하고 적용 사례를 통하여 코드 이동성에 근거한 기능 합성의 예를 제시하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10c
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• pp.652-654
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• 2001

지니(Jini)는 썬 마이크로 시스템즈에서 제안하고 있는 확장성 있고 견고함을 가진 분산 시스템을 구축하기 위한 구조이다. 지니(Jini) 서비스들은 하나 또는 그 이상의 자바 언어 인터페이스와 클래스들에 의해 정의된다. 이것은 하드웨어나 소프트웨어의 구현에 상관없이 지니 서비스를 사용하는 기기들 사이에서 동적인 상호작용을 생성시키고 네트워크를 통해 서비스를 전달한다. 일단 기기들이 특정한 하드웨어에 구애 받지 않고 각종 디바이스를 통해서 네트워크에 접속이 이루어지면 시간과 장소에 상관없이 각종 서비스를 받을 수 있게 된다. 본 논문에서는 스케줄링과 방향 재설정을 통해 지니에서의 부하를 분산 시키는 방법으로 보다 효율적인 서비스를 받을 수 있는 모델을 제시한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.3
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• pp.715-723
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• 2015

In this paper, we propose a context-awareness routing algorithm DDV (Dynamic Direction Vector)-hop algorithm in Mobile Ad Hoc Networks. The existing algorithm in MANET, it has a vulnerability that the dynamic network topology and the absence of network expandability of mobility of nodes. The proposed algorithm performs cluster formation using a range of direction and threshold of velocity for the base-station, we calculate the exchange of the cluster head node probability using the direction and velocity for maintaining cluster formation. The DDV algorithm forms a cluster based on the cluster head node. As a result of simulation, our scheme could maintain the proper number of cluster and cluster members regardless of topology changes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6B
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• pp.534-543
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• 2006

As the topology frequently varies, more cluster reconstructing is needed and also management overheads increase in the wireless ad hoc/sensor networks. In this paper, we propose a multi-hop clustering algorithm for wireless sensor network topology management using dynamic pre-clusterhead scheme to solve cluster reconstruction and load balancing problems. The proposed scheme uses weight map that is composed with power level and mobility, to choose pre-clusterhead and construct multi-hop cluster. A clusterhead has a weight map and threshold to hand over functions of clusterhead to pre-clusterhead. As a result of simulation, our algorithm can reduce overheads and provide more load balancing well. Moreover, our scheme can maintain the proper number of clusters and cluster members regardless of topology changes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5A
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• pp.348-357
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• 2012

Recently, smartphone, notebook, PC and other supporting wireless LAN device have come into wide use. By increasing user that use wireless LAN device, wireless traffic also increased. If wireless traffic through one AP is increase, it causes throughput decrease. To solve this problem, wireless LAN service provider install more AP where overload occurred. But this is not enough. Because stations can't know AP's load factor, and APs do nothing for load balancing. In this paper, we propose Multi-Interface Access Point(MIAP) to solve this problem. MIAP operate same as multiple APs with multi-interface, and MIAP measure each interface's load periodically. If MIAP detect overloaded interface, MIAP transfer station from overloaded interface to under-loaded interface. We conducted an experiment for verifying existing problem, and we found this problem occurred. We plan an experiment scenario for a comparison between existing AP and MIAP, and excute these experiment. In the result, we show MIAP with load balancing can improve total throughput about 72% and stabilize delay jitter than existing AP.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.28-30
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• 2005

센서들은 제한된 자원으로 구동되므로 오류가 나기 쉽다. 특히 구조적 라우팅의 경우 클러스터 헤드의 오류시 많은 수의 센서가 네트워크에서 분리되어 네트워크 성능에 악영향을 미친다. 따라서 오류 처리에 관한 연구들이 이루어져 왔으나 기존의 연구들은 망을 최적으로 유지하기 위해 재구성시 전체 네트워크를 재구성 하며 고정된 주기를 사용하여 전체적인 망이 최적의 상태임에도 불구하고 재구성 되거나, 클러스터에 오류가 생겨도 재구성되기까지 기다려야 한다는 단점이 있었다. 따라서 본 논문에서는 지역적인 재클러스터링을 통하여 네트워크를 최적으로 유지하며 클러스터들의 부하를 고려하여 망을 동적으로 재구성 하는 방법을 제안하였다. NS-2를 이용한 시뮬레이션을 통하여 기존의 방법에 비하여 본 논문에서 제안한 알고리즘이 네트워크 유지시간을 연장시켜 더 많은 양의 데이터가 수집됨을 확인 할 수 있었다.